Soil retention, protection of natural and artificial structures, and increased land use are only a few reasons Which motivate the use of landscape structures. For example, soil is often preserved on a hillside by maintaining the foliage across that plane. Root systems from trees, shrubs, grass, and other naturally occurring plant life work to hold the soil in place against the forces of wind and water. However, when reliance on natural mechanisms is not possible or practical man often resorts to the use of artificial mechanisms such as retaining walls.
In constructing retaining walls many different materials may be used depending upon the given application. If a retaining wall is intended to be used to support the construction of an interstate roadway, steel or a concrete and steel retaining wall may be appropriate. However, if the retaining wall is intended to landscape and conserve soil around a residential or commercial structure a material may be used which compliments the architectural style of the structure such as wood timbers or concrete block.
Of all these materials, concrete block has received wide and popular acceptance for use in the construction of retaining walls and the like. Blocks used for these purposes include those disclosed by Risi et al, U.S. Pat. Nos. 4,490,075 and Des. 280,024 and Forsberg, U.S. Pat. Nos. 4,802,320 and Des. 296,007 among others. Blocks have also been patterned and weighted so that they may be used to construct a wall which will stabilize the landscape by the shear weight of the blocks. These systems are often designedto "setback" at an angle to counter the pressure of the soil behind the wall. Setback is generally considered the distance which one course of a wall extends beyond the front of the next highest course of the same wall. Given blocks of the same proportion, setback may also be regarded as the distance which the back surface of a higher course of blocks extends backwards in relation to the back surface of the lower wall courses. In vertical structures such as retaining walls, stability is dependent upon the setback between courses and the weight of the blocks.
For example, Schmitt, U.S. Pat. No. 2,313,363 discloses a retaining wall block having a tongue or lip which secures the block in place and provides a certain amount of setback from one course to the next. The thickness of the Schmitt tongue-or lip at the plane of the lower surface of the block determines the setback of the blocks. However, smaller blocks have to be made with smaller tongues or flanges in order to avoid compromising the structural integrity of the wall with excessive setback. Manufacturing smaller blocks having smaller tongues using conventional techniques results in a block tongue or lip having inadequate structural integrity. Concurrently, reducing the size of the tongue or flange with prior processes may weaken and compromise this element of the block, the course, or even the entire wall.
Previously, block molds were used which required that the block elements such as a flange be formed from block mix or fill which was forced through the cavity of the mold into certain patterned voids within the press stamp or mold. The patterned voids ultimately become the external features of the block body. These processes relied on the even flow of a highly viscous and abrasive fill throughout the mold, while also not allowing for under-filling of the mold, air pockets in the fill or the mold, or any other inaccuracies which often occur in block processing.
The result was often that a block was produced having a well compressed, strong block body having weak exterior features. Any features formed on the block were substantially weaker due to the lack of uniform pressure applied to all elements of the block during formation. In turn, weaker exterior features on the outside of the block such as an interlocking flange could compromise the entire utility of the block if they crumble or otherwise deteriorate due to improper formation.
The current design of pinless, mortarless masonry blocks generally also fails to resolve other problems such as the ability to construct walls which follow the natural contour of the landscape in a radial or serpentine pattern. Previous blocks also have failed to provide a system allowing the use of anchoring mechanisms which may be affixed to the blocks without complex pinning or strapping fixtures. Besides being complex, these pin systems often rely on only one strand or section of a support tether which, if broken, may completely compromise the structural integrity of the wall. Reliance on such complex fixtures often discourages the use of retaining wall systems by the every day homeowner. Commercial landscapers generally avoid complex retaining wall systems as the time and expense involved in constructing these systems is not supportable given the price at which landscaping services are sold.
As can be seen the present state of the art of forming masonry blocks as well as the design and use of these blocks to build structure has definite shortcomings.